Custom Event Schemas

Define and validate custom event payloads.

OpenSend can store schema-like metadata for custom events so automations use predictable payload shapes.

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This page is intentionally concise. Use the neighboring guides below for the next implementation details, route contracts, or operational steps.

Agent Email Inbox Skill

Build an agent inbox on top of OpenSend receiving without exposing raw mailbox access to the agent runtime.

React Email Skill

Build HTML email with React components.

Email Best Practices Skill

Guardrails for production email systems.

Migrate from Resend

Use the in-tree OpenSend migration verifier to inspect an existing Resend integration before you point it at OpenSend. Always pass the application repository you want to scan; the verifier fails closed when the target directory is omitted.

Send emails with Java and Kotlin

Use the first-party OpenSend JVM SDK from plain Java, Kotlin, Spring Boot services, workers, and command-line applications. The package lives in this repository at packages/jvm-sdk while registry publishing is prepared. This is a partial, blocking-only SDK for emails, contacts, domains, and suppressions; use the REST API and /openapi.json for other resources.

Send emails with PHP

Send email from PHP with the first-party OpenSend PHP SDK. This first SDK slice is send-only: it supports the single-email send method, idempotency keys, typed request/response objects, and typed OpenSend API errors, but not other OpenSend resources yet.